NERDC COST EFFECTIVE HOUSING TECHNOLOGY

NERDC introduced alternative methods for wall construction

1. Slip form wall (seamless cast – insitu walls) i. cement and quarry dust

ii. cement and soil 2. Soil cement block masonry wall

i. cement soil blocks

1. (i)Slip-form walls with cement & quarry dust

Mix: Cement and Quarry dust 1:12 Water: small volume to get the correct consistency of mix

A steel shutter (form) is needed

Slip form wall for multi storied buildings

1. (ii)Slip form wall construction using cement & soil

• Slip-form wall constructed with cement and soil instead of cement &

quarry dust

• Special attention is needed for following aspects. 1. Condition of the soil

2. Cement to soil ratio. 3. particle size distribution of soil

4. Water Content 5. Uniformity of mixing

Slip form wall cement/soil

2. Compressed Stabilized Earth Blocks (CSEB)

Cement stabilized earth blocks are used an alternative building material for burnt clay bricks and cement, sand blocks. This is an appropriate and cost-effective wall

construction material as most of the generally available sandy soil and gravel soil can be used for manufacturing of these blocks. Soil can easily be extracted and easily processed

for production of these blocks. Soil is mixed in certain proportions of cement (5-10%) for producing these blocks. Unlike normal clay bricks, burning is not necessary. Unlike cement sand blocks river sand is not necessary. Hence, low energy consumption and low

environmental pollution or degradation occurs with the production of these blocks.

Requirements

Clay + slit < 40% Sand + gravel >60%

Sieving of Soil

3. Sieve soil form 6mm mesh or 12mm mesh keeping with 55’-60’ to get good finish blocks for walls to use without plaster.

4. If plasters are going to apply both sides of wall, sieving of soil from 12mm mesh is enough to manufacture the blocks.

How to add cement for soil

Cement soil mix proportion is depended upon the capability of block manufacturing machine. Such as method of compact and amount of compaction. So, the cement: soil mix proportions vary with machines as below.

1. Vibrated type Cement : Soil

- (normal block machine)

2. Rammed type Cement : Soil

- (hand mould, hand rammed machine)

3. Compressed type a) Manual type : Cement : Soil

(Hand compressed machine) b) Hydraulic type : Cement : Soil

(Hydraulic compressed machine) 100 blocks per hour After mixing soil with cement properly, next add water to mix.

Manufacturing of Blocks It is better to used compressed machines to get good finish blocks which can be used

without wall plastering.

Curing with Water

Keep blocks under shade (or cover with blade polytheen)

Cure 14 days (3 times per day)

It is better to cure blocks by sprinkling water

Keep another 14 days to shrinkage

Then, use the blocks after testing

Strength of Blocks

According to the SLS, minimum compressive strength of blocks should be higher than 1.2 N/m2 and that can be used to single story building and partition walls. Sieve and compression strength of blocks for load bearing walls can be selected according to the

SLS standard.

Special Things to be kept in Mind Factors affected for the block strength

ii. Type of machine and level of compaction iii. Type of soil

iv. Amount of cement degree of mixing soil with cement Quantity of water (optimum water content) Curing (frequency of curing and curing period)

Mortar for block laying and wall plaster No need plaster for good finish wall. Then it can be apply early pa int on wall after block

layer. If any one wants to plaster wall, same mortar mix used for block laying can be used to plaster also.

Soil should be sieved for 3mm mesh and

(a) 1:3:3 cement, soil (clayey soil) sand mortar can be used to plaster and block

laying 1:15 cement and clay (from same soil or makulu soil) can be used to

smooth plaster or

(b) 1:6 cement, soil (sandy soil) mortar can be used to plaster and block laying

1:15 cement and clay (from same soil or makulu soil) can be used to smooth

plaster or

(c) 1:5 or 1:6 cement sand mortar for wall construction

1:1:5 cement lime and sand for plaster and lime for smooth plaster

and also,

1:2 cement: soil (soil should be sieved form 2mm mesh) paste can be used to apply in faces of interlocking blocks to be laid in walls.

Application of paint

Natural soil colour paint

Plain makulu soil or clay soil or soil used for blocks in water and stir well and

use sterner to separate clayey liquid

Add cement 250 ml and 250 ml chemifix or good binding gum to 8L clayey liquid and stir well.

Apply two or three coats on walls using a brush. Before applying paint, wall should be prepared well.

Applying or spraying two coats of matt clear warnish on wall, it can be provided additional protecting coat to the wall. (Also it can be used paints

given in SLS standard)

Application of clay base colour paints

Solve makulu soil or clayey soil or soil used for block manufacturing, in water.

Pure water to gunny bag placed on sand pile and separate clay from water.

Keep clay under sunlight to dry well.

Crush dried clay particle in to powder by rollers or a machine.

Take colour cement one part and mix with 15 parts of clay powder well.

Next take 16 part of water and mix with one part of good binder gum well.

Next dissolve prepared colour powder in prepared binding liquid and stir well.

Next apply two or three coats on walls prepared correctly.

Also, it can be applied emulsion and weather shield paints available at market.

Advantages:

Solution for sand crisis Environmentally friendly green product (no problem related to

sand mining, no problem related to deforesting and clay mining) Freely available, so less transport problems

Comfortable environment in house (low heat in house) so much

better for dry season and dry zones. Simple technology and simple machines

15%-50% cost can be saved (according to availability of soil) Creating new employments

Disadvantages:

If technology is not used in proper way, it may occur some problems

Man power requirement is dependent upon the type of soil